<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>版心布局</title>
  <meta name="viewport"
    content="width=device-width, initial-scale=1.0,maximum-scale=1,minimum-scale=1,user-scalable=no">
  <script> (function flexible(window, document) { var docEl = document.documentElement; var dpr = window.devicePixelRatio || 1; function setBodyFontSize() { if (document.body) { document.body.style.fontSize = 12 * dpr + "px"; } else { document.addEventListener("DOMContentLoaded", setBodyFontSize); } } setBodyFontSize(); function setRemUnit() { var rem = docEl.clientWidth / 10; docEl.style.fontSize = rem + "px"; } setRemUnit(); window.addEventListener("resize", setRemUnit); window.addEventListener("pageshow", function (e) { if (e.persisted) { setRemUnit(); } }); if (dpr >= 2) { var fakeBody = document.createElement("body"); var testElement = document.createElement("div"); testElement.style.border = ".5px solid transparent"; fakeBody.appendChild(testElement); docEl.appendChild(fakeBody); if (testElement.offsetHeight === 1) { docEl.classList.add("hairlines"); } docEl.removeChild(fakeBody); } })(window, document); </script>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    div {
      width: calc(100rem / 64);
      height: calc(100rem / 64);
      font-size: calc(100rem / 64);
      background-color: aqua;
    }
  </style>
</head>

<body>
  <div>

  </div>
  <script>
    window.onload = function () {
      setFont();
      window.addEventListener("resize", function () {

        setFont();
      })
      function setFont() {
        var div = document.querySelector("div");
        div.style.fontSize = document.querySelector("html").style.fontSize;
        div.innerHTML = "html的字体大小为" + document.querySelector("html").style.fontSize;
      }

    }
  </script>
</body>

</html>